The research team tested whether migratory songbirds observe the anti-predator behaviour of local birds, which are familiar with local predators. One common form of this self-protecting behaviour is "mobbing": The birds approach a potential predator, rapidly changing position around its location and performing restless wing and tail movements while emitting loud, broad-frequency calls. These calls are easily recognizable and act as signals of threat.

Because migrating birds rarely participate in mobs, the researchers speculate that they may gain information about predator location, identity and degree of threat through listening to mob calls of other species residing in the area. To test this theory, they broadcast playbacks of alarm calls that were familiar (black-capped chickadee, common in North America) and foreign (blue-gray tanager, common in Central America) to birds migrating between Canada and Belize.

The Belizean resident birds responded only to the tanager calls, but migrant birds responded to both the tanagers and the chickadees.

There remains some research to demonstrate the hypothesis; the research team still wants to test the reaction of migrant birds wintering in Belize against the behavior of those same migrants along their fall migration path. Still, this is an intriguing result. It is one more reason why it is silly to use "bird brain" as an insult. Animals have much better learning capabilities than many people realize.

A question that frequently arises among birders is what happens to vagrant or extralimital birds when they fly off course. Some hold that their lives are nasty and short; others point to examples of rare birds persisting for long periods at a single location. (I tend to fall into the latter group, though I can see arguments for both.) If migrants can observe the behavior of local birds and learn from them, it provides some hope that vagrant birds might be able to do so as well.